Every “big data” data source I have ever worked with is already filled to the brim with low-quality, obviously wrong data. I have to think that is also true of the data scraped or collected by the big companies. I don’t think it matters that the personal data they collect is wrong, so long as they can convince ad buyers that it is accurate.
I went to one for a candidate for the House district I lived in a few election cycles ago, It was mostly stump speeches and other “rah rah we’re gonna win!” style pontificating. But one thing I did not expect and I actually found interesting was the house candidate spent a lot of time introducing other local politicians that were in down ballot races in the district. City council seats, education board seats etc. That turned out to be really useful, because it meant I got to meet/ hear from candidates who I either had no idea existed or who were just a name of a flyer before then. I suppose that experience may not transfer to a national candidate rally though.
This is not that funny but I was amused watching it happen. One time I was at the DMV in a college town and a kid was at the counter trying to get his license renewed. From what I could gather he had it revoked because he was underage and had a DUI. Lady at the counter bounced the kid and a few minutes later, the kid came back in with his father and they were apparently from a rich family. Or at least rich by Ohio standards. When the lady at the counter explained that he could not have his license renewed because he had a court order against him, the father started in on the “Do you know who I am? I will buy this whole town!” routine, but the DMV lady was not having any of it. Both the kid and the father insisted that the judge did not have any right to take his license away from him and that it would be over turned on appeal so the DMV lady had to give him his license, because dad would make sure she got fired if he didn’t. But the DMV lady would not relent and issue a license. The father and kid were getting pretty animated, so finally the lady picked up the phone and said something to the effect of “Your kid lied on this form and is probably violating his probation, we can call the court right now and see what your judge thinks about that.” Which at that point caused them to sheepishly leave. When I got to the counter she told me that was not the first time in her career someone tried to do that to her.